Conventionally, as a method of manually operating a robot, there are (1) an individual-axis manual feed for respective joint axes of a robot, (2) multi-directional manual linear feed in the perpendicular XYZ coordinate system defined in the working space of a robot, (3) manual linear feed in each axial direction in a perpendicular tool coordinate system defined for a wrist section of the distal end of a robot arm, and (4) manual feed for hand inclination control in the perpendicular coordinate system, and manual feed for the hand inclination control in the tool coordinate system. In practice, the required manual feed has to be carried out by first selecting one coordinate system for execution of these manual feed procedures and then selecting one axis being subject to such manual feed as well as its feed direction (+, -) Thus, it is necessary for the operator, before starting the operation of a robot, to check the exact direction of operation; based on the present attitude and coordinate system of the robot. This check is done depending on the operator's empirical perception. To do this, for example, the operator may first operate the robot to let it move a little to verify the resulting direction of movement, and then gives thereto a necessary operation command for the subsequent operation.
However, with such an operation control system, it may happen that the robot accidentally operates in directions operator did not expect. If this is the case, in the prior art, the operator is required to restart the operation by restoring the initial position and attitude of the robot manually. However, since the stored initial state information is lost when the robot is operated once, it has been difficult to restore the robot to its initial state accurately. This contributes to the complication of the work.
According to the prior known system, since the robot typically operates at a certain speed determined based on the override value set at the time of start, in those cases where this speed is greater than the operator's expected operation speed, there arises a risk of occurrence of work errors.
Furthermore, in the case of the prior art, when the preset overriding speed is too fast to verify the operating direction at the start of operation, it is required to check operating direction by once lowering the preset overriding speed, and thereafter restarting the intended work after returning the overriding speed to the set value. This adversely affects the working efficiency.